The present invention is an improved cable guide for the selector mechanism of an elevator system.
With elevators used for vertical transportation, it is common to reproduce the position and motion of the car remotely and on a smaller scale with a device driven by the car. This device is known in the industry as a selector. The simulated car position in the selector is used as an input of various control systems for the elevator drive system.
A typical drive for an elevator selector mechanism is a cable loop which is disposed in the hoistway parallel to the direction of movement of the elevator car. Portions of the cable extend in opposite directions from the car, up and down in the shaft, respectively, and are deflected from the top and bottom of the shaft to a common input drive of the selector. The cable is attached to the elevator car so that motion of the car moves the cable and thereby the selector input.
Since no slippage can be tolerated, the cable must be attached relative to the selector input. Typically, the cable is attached to a storage take-up drum of sufficient size to allow the full travel of the car. The two cable portions, arriving from the top and bottom of the elevator shaft, are connected to the drum to wind in opposite rotational directions of the drum. Rotation of the drum thereby causes one cable portion to wind and causes the other cable portion synchronously to unwind. The cable portions are attached to opposite ends of the drum and wound in sequential rows, across the drum, toward one another.
As the cable feeds on and off the storage drum, the leads, of necessity, travel from side to side across the surface of the drum. This lateral motion complicates running the cable to and from the car, particularly in cramped areas, a problem which has plagued the industry for many years.
In an effort to alleviate the problems inherent in feeding cable from a drum, some companies have abandoned the use of cables in favor of chain or tape drives. However, such drives are less flexible, more expensive, and susceptible to breakage. Other devices such as floating idler sheaves are in common use, but at best such devices only reduce the difficulties and are themselves a problem to maintain.